It is known that III-N based devices, such as GaN semiconductor devices, grown on a silicon substrate require gate dielectric material with sufficient dielectric constant and a proper band offset for good operating characteristics, e.g. low leakage currents and good gate control. In the prior art some attempts at using high-k polycrystalline materials have been unsuccessful. For example, polycrystalline Hf2O3 has been proposed for a gate dielectric. However, the material was found to be unsuitable because of leakage current paths via nanocrystallite grain boundaries and because crystal defects induce high interface state density which deteriorate electrical properties of the material.
Using Er2O3 as a gate dielectric to reduce leakage current in an MOS-HEMI device has been proposed by Lin et al. (“Physical and electrical characteristics of AlGaN/GaN metal-oxide semiconductor high-electron-mobility transistors with rare earth Er2O3 as a gate dielectric”, Thin Solid Films, Vol. 544, pp. 526-529, (2013)). However, the HEMI is fabricated on a silicon substrate using an AlN buffer on which to grow the GaN base.
Using Sc2O3 as a gate dielectric to reduce leakage current in an MOS-HEMI device has been proposed by Mehandru et al. (“AlGaN/GaN metal-oxide-semiconductor high electron mobility transistors using Sc2O3 as the gate oxide and surface passivation”, Applied Physics Letters, Vol. 82, No. 15, PP. 2530-2532, (14 Apr. 2003)). However, no mention is included as to the substrate (wafer) used.
In the semiconductor industry, it is known that growing III-N material, such as GaN, on a silicon substrate is difficult due in large part to the large crystal lattice mismatch (−16.9%) and the thermal mismatch (53%) between silicon and GaN. Thus, some type of buffer layer or layers is generally formed on the silicon substrate and the III-N material is grown on the buffer layer. Generally, the prior art buffer layers are either complicated and expensive to form or do not adequately reduce the strain in the GaN due to crystal lattice mismatch.
It would be highly advantageous, therefore, to remedy the foregoing and other deficiencies inherent in the prior art.
Accordingly, it is an object of the present invention to provide new and improved methods for the growth of heterostructures for use in semiconductor devices on silicon substrates.
It is another object of the present invention to provide new and improved methods for the growth of heterostructures on a silicon substrate for use in semiconductor devices and the growth of a template and gate dielectrics in the devices that provides stress/strain to enhance 2DEG carrier density.
It is another object of the present invention to provide new and improved gate dielectrics and new and improved methods for the growth of gate dielectrics for III-N devices on silicon substrates.
It is another object of the present invention to provide new and improved methods for the growth of III-N devices on a silicon substrate that includes engineered stress/strain in the final III-N material.